This invention relates to apparatus for compression crimping fibrous material. More particularly, the invention relates to such apparatus having a pair of movable members, each of the members having a face substantially opposed to a face of the other, the faces defining lateral walls of the compression crimping zone of the apparatus and being biased toward each other to restrict egress of the fibrous material from the zone and thereby exert a back pressure on the fibrous material, causing the fibrous material to buckle, form a plug in the zone and thereby crimp in the zone.
Various apparatuses for compression crimping fibrous material can be provided which comprise means defining a compression crimping zone, means for feeding fibrous material into the compression crimping zone and a pair of movable members, commonly known as "pressure shoes," each having a face substantially opposed to a face of the other, the faces defining lateral walls of the zone and being biased toward each other to restrict egress of the fibrous material from the zone and thereby exert a back pressure on the fibrous material, causing the fibrous material to buckle, form a plug in the zone and thereby crimp in the zone. The shoes can be biased toward each other with a substantially constant force. Under the influence of the plug of yarn which is formed in the crimping zone, the shoes oscillate slightly. The apparatus can also include means defining a pair of opposed, stationary walls between which the shoes oscillate in planes parallel to the stationary walls. The stationary walls can abut the sides of the shoes in order to prevent the plug from escaping laterally from between the substantially opposed faces of the shoes. It is found that some of the filaments of the fibrous material of which the plug is constituted will now and then be caught between a shoe and one or the other of the aforementioned stationary walls. Undesired, uncontrolled tension is created in the plug and particularly in the filaments which have been caught, resulting in a lower degree of crimping. Moreover, the filaments which are caught may be damaged.
Another problem inherent in the arrangement of stationary walls abutting the shoes arises from the fact that a finish composition generally is applied to the fibrous material before the fibrous material is fed into the crimping apparatus. The finish composition lubricates the surfaces of the fibrous material and may also have anti-static properties, thereby facilitating the processing of the fibrous material. However, some of the finish composition, which rubs off the fibrous material, accumulates between the shoes and the abutting stationary walls. Similarly, pieces of broken filament and other debris accumulate between the shoes and the abutting stationary walls. This impedes oscillation of the shoes, which oscillation is essential in order that the shoes adjust to transient changes in the plug configuration or position thereby to provide substantially constant crimping conditions. One negative result, for example, is that, the effective pressure applied by the shoes may gradually decrease as the build-up of finish, pieces of broken filament and other debris between the shoes and the stationary walls decreases the force applied to the plug by the shoes.
It is an object of the present invention to provide an improvement in apparatus of the aforementioned type thereby to eliminate the problems described above.
Other objects and advantages of the invention will be apparent to one skilled in the art from the following description of the invention.